Various fire-retardant products are available for use in furniture, mattresses, etc. These products are made using natural or synthetic fibers to form the basis of the fabric, which can be woven, spunlace nonwoven or knit.
Fire resistance can be imparted to fibers in several ways. For example, fabric can be treated with chemicals to render it fire-retardant. However, the process of chemical treatment can weaken the fabric, causing it to crack when exposed to direct flame. Once the outlying fabric is damaged, the flame can come into contact with the underlying material, causing it to ignite. Also, treated fabrics are heavy and do not last as long as non-treated fabrics.
Other fabrics are available in the art that are not as susceptible to cracking and can withstand open flame tests. One example is a 100% fiberglass flame barrier coating a woven polymer, but fiberglass barriers have low durability due to glass-to-glass abrasion. Another option is a woven or knit core-spun yarn based flame barrier, where natural and/or synthetic fibers are wrapped around a fiberglass core, a multifilament core, or a core yarn. The fibers may be treated with a fire retardant chemical or a coating of thermoplastic polyvinyl halide composition.
Woven flame barriers suffer drawbacks in becoming very stiff when coated with fire retardant materials, making the final product less comfortable/desirable to a consumer. Also, woven and nonwoven knit flame barriers must be laminated to a decorative fabric or double upholstered during manufacturing, increasing costs.
Another disadvantage of chemically treated fire retardant material is that the treatment adds weight to the fabric, making an already cumbersome product even more difficult to handle. Also, many chemical treatments are water soluble or otherwise impermanent. Water solubility is a drawback, making the material less durable. Chemical treatment can also be costly. Thus, there is a need in the art for a lightweight fire retardant barrier that does not require chemical treatment.
Regarding nonwoven technology, fibers are bought from suppliers, usually referenced by a brand name or generic name. The fibers are carded to straighten out the fibers. Layers of carded fibers are cross lapped (one layer running north/south, then another layer running east west) over one another to build a batt. The fiber batt is then densified by either thermal bonding, needle punching, or spray bonding. Thermal bonding may be accomplished by adding low melt fibers that have a lower melting point than the other fibers and by heating the batt such that the low melt fibers melt. These fibers act as an adhesive in a web because their softening point is less than the softening point of the other fibers in the material. Needle punching involves punching a needle plate repeatedly through the batt to physically entangle the fiber layers. Typically, the more the batt is needled, the lower the loft and the higher the strength. The loft of the nonwoven can be set by the amount of needlepunching applied. With thermally bonded material, loft can be controlled by compressing the batt in the oven and blowing air through the batt as the batt is cooled. Spray bonding may be accomplished by spraying a liquid binder (e.g. latex) onto one or both sides of the carded batt and drying and curing the batt in an oven. The nonwovens are then cut and rolled for sale to manufacturers for incorporation into products such as mattresses, furniture, etc.
WO 03/023108 describes a nonwoven highloft flame barrier which uses a blend of inherently flame retardant fibers and modacrylic fibers, i.e. fibers extruded from polymers made from halogenated monomers. However, modacrylic fibers are expensive, making it difficult to provide high quality, low cost products to consumers.
U.S. Patent Application Publication No 2004/0097516A1 describes a fire retardant nonwoven fabric for use in household goods. However, the nonwoven fabrics disclosed in the publication include more than one type of fire retardant fiber and/or a fire retardant resin used to coat fibers. The disclosed materials also use higher denier fibers and polyethylene terephthalate, which are not advantageous for flame barrier and cost efficiency.
Prior fire retardant materials generally have been produced with higher basis weight, e.g. in the 0.75-1.25 osf range for highloft barriers, and generally use relatively high denier fibers. When lower basis weight materials are produced, the material must be densified in order to increase fire resistance or charring, resulting in a product that does not have the soft feel desired for mattresses and other products. Thus, there is a further need in the art for a high loft flame barrier that retains feel characteristics desirable of mattresses, bedspreads, and the like.